Multiservice switches used, for example, by communications providers in wide area networks typically provide a number of different interfaces for incoming and outgoing communications traffic to the core switching fabric in order to accommodate customer needs. These interfaces can range, for example, from high rate optical trunking ports to lower rate electrical interfaces. In general, the different interfaces are provided through service specific equipment grouped together on what are termed “service shelves”, where the service shelves then couple to the switching core. A typical service shelf will include the physical layer interface which couples to higher layer service cards (e.g. layer 2 or 3 for ATM or IP) and then to the switching core. Failure protection of equipment utilized in multiservice switches usually in the form of redundant circuit paths is also extremely important in order to provide the type of reliability that is necessary for these switches. That is, the ability to detect faults in a packet switching system and restore service quickly is an important issue in overall availability to the customer. Extra service cards (or protection cards) and even redundant switching cores are often provided within a service shelf to allow for the required fault protection.
In prior art multiservice switches of the type described above, when a fault is detected in a communications link within the switch, entire shelves of service cards or entire switching cores are required to be switched in response to the detected fault. This causes interruptions on all portions of the switching system beyond those that have failed. This is a disadvantage in that the greater the number of communications links that are affected, the greater the chance is that data will be lost or communications will be disrupted during or as a result of the switchover. Accordingly, there is a need to provide a system that better isolates failures in one part of the system from other areas of the packet switching system.